In the last funding period of this grant special attention will be given to identify specific functions of the ribophorins and of other microsomal components. Attempts will be made to correlate modifications of microsomal membranes by proteolytic enzymes, alcylating agents and of sulfhydryl reagents with in vitro ribosome binding, with the efficiency of vectorial discharge and with co- and postranslational modifications of proteins made on membrane bound polysomes. Antibodies against the ribophorins will be used in attempts to inhibit specific functions in the multi step process of vectorial discharge. It is also planned to continue the promising studies on the biosynthesis of ribophorin and of their cotranslational insertion into microsomal membranes.